With reduced costs of broadband networks in recent years, many data distribution systems have been created, in which large displays are installed in stores throughout the city and/or in vending machines, and high-resolution videos such as information or advertisements for a particular area are distributed from a center server. These distribution systems include systems that distribute predetermined contents to display apparatuses at preset times, and systems in which display apparatuses acquire contents from a center server periodically or in response to an acquisition instruction from a user as a trigger.
Particularly, in the latter case, information that matches the tastes and interests of the user viewing the information can be displayed, so such systems are expected to increase in the future. However, there are problems in which, due to communication delays in the network between the center server and a display apparatus, there are cases where the user may leave the spot before the contents are displayed.
As one method for shortening the time until contents are displayed, there is a method of arranging a cache server near the display apparatuses, and distributing contents from that cache server. When many display apparatuses are distributed, plural cache servers are also installed, however, when there are contents in the cache server for a user that is currently at a display apparatus, it is possible to shorten the time necessary for displaying the contents. However, when there are no contents in a cache server for the user, the cache server acquires contents from the center server. Therefore, it still takes time.
The following technique has been proposed for solving this kind of problem concerning a time required for the display. That is, the center server obtains an event that represents that a user has come closer to a display apparatus from an entrance and exit system of a building and the like, and distributes contents beforehand for that user to a cache server near the display apparatus, in response to that event as a trigger. As a result, when the user causes the display apparatus to read the user ID by holding up an IC card or the like in front of the display apparatus, the contents can be displayed right away.
However, in this technique, an event from the entrance and exit system is directly transmitted to the center server, so as the number of users using the system increases, events become concentrated at the center server, and sometimes the processing speed of the center server decreases. Moreover, there is a limit to a capacity of the cache server, so preferably caching of contents that wastes resources in the cache servers is avoided.
Namely, there is no technique for improving the efficiency of a system that outputs contents data, which matches each user, at plural display apparatuses.